Trisomy 21, also known as congenital dysgenesis, is most commonly a birth defect-like disorder caused by chromosomal aberrations. The disease is mainly caused by congenital factors and has a specific phenotype of mental retardation. The main clinical features are mental retardation, physical retardation and peculiar facial features, most of which are associated with cardiac malformations. These patients are less resistant to disease and are only able to perform simple tasks due to their low intelligence, and in severe cases, they are unable to take care of themselves and become a burden to society and their families. Therefore, Down’s syndrome screening is very important. In China, most women of childbearing age are no longer screened for Down’s syndrome at the age of 35 or older, and non-invasive DNA or amniocentesis is recommended to screen for Down’s syndrome to avoid the impact on society and families.